public void GetCountOfPhotosShouldWorkCorrectly() { var photos = new List <Photo>(); var mockPhoto = new Mock <IDeletableEntityRepository <Photo> >(); mockPhoto.Setup(x => x.All()).Returns(photos.AsQueryable()); mockPhoto.Setup(x => x.AddAsync(It.IsAny <Photo>())).Callback((Photo ph) => photos.Add(ph)); var service = new AdminsService(null, null, mockPhoto.Object, null, null); var photo = new Photo { Id = "1", ImagePath = "/images/photos", }; photos.Add(photo); var expectedResult = 1; var result = service.GetCountOfPhotos(); Assert.Equal(expectedResult, result); }